package previous.Test_0401;

import java.util.*;

/**
 * Created with Intellij IDEA
 * Description:
 * User: 星辰
 */
public class Bridge_Blue {
    //刷题统计
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        //在此输入您的代码...
        long a=scan.nextLong();
        long b=scan.nextLong();
        long n=scan.nextLong();
        long c=(a*5+b*2);
        long day=0;
        day=n/c;
        day*=7;
        n=n-day*c;

        for(int i=1;i<=7;i++) {
            if(i<=5) {
                if(n<=0) {
                    break;
                }
                n-=a;
                day++;

            }else {
                if(n<=0) {
                    break;
                }
                n-=b;
                day++;

            }
        }
        System.out.println(day);
        scan.close();
    }
    //九进制转十进制
    public static void main2(String[] args) {
        Scanner scan = new Scanner(System.in);
        //在此输入您的代码...
        int x=Integer.parseInt("2022",9);
        System.out.println(x);
        scan.close();
    }
    static int[] a;
    static double m;
    static int n;
    static int minCut;
    public static void main1(String[] args) {
        Scanner scan = new Scanner(System.in);
        //在此输入您的代码...
        n=scan.nextInt();
        m=scan.nextInt();
        a=new int[n];
        minCut=Integer.MAX_VALUE;
        for(int i=0;i<n;i++) {
            a[i]=scan.nextInt();
        }
        Arrays.sort(a);
        for(int i=0;i<n/2;i++) {
            int tmp=0;
            tmp=a[i];
            a[i]=a[n-i-1];
            a[n-i-1]=tmp;
        }
        dfs(0,0,0);
        if(minCut==Integer.MAX_VALUE) {
            System.out.println(-1);
        }else {
            System.out.println(minCut);
        }
        scan.close();
    }
    public static void dfs(double sum,int i,int cut) {
        //如果sum>m,返回
        if(sum>m || cut>minCut) return;
        if(sum==m) {
            minCut=Math.min(minCut, cut);
            return ;
        }
        if(i>=n) return;
        //不选，不切
        dfs( sum, i+1,cut);
        //选，不切
        dfs( sum+a[i], i+1,cut);
        //选，切
        dfs(sum+a[i]/2.0,i+1,cut+1);

    }
}
